The padlock can be lubricated with WD-40 or a similar lubricant and the key may work again. If the lubricant fails, you can try to pick the lock. As a last resort, you could cut the lock off.
You can try to call a locksmith to help you open your padlock. If you have any skill in lock picking you could also try it.sometimes, you can usually pick a simple tumbler lock with minimal skill.
First thing to try is shooting some kind of light lubricant such as WD40 into the lock mechanism. If that doesn't work either use a lock pick or a boltcutter.
First check to make sure you are using the right key. If it is cold weather what you want to do is warm up the lock either with warm water or hold a lighter up to it so it can warm up. Then try the lock.
